From: Andi Kleen <andi@firstfloor.org>
To: Jesper Dangaard Brouer <jbrouer@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>,
linux-perf-users@vger.kernel.org,
Daniel Borkmann <dborkman@redhat.com>,
Florian Westphal <fw@strlen.de>,
Hannes Frederic Sowa <hannes@stressinduktion.org>
Subject: Re: Use of PMU counters inside kernel?
Date: Thu, 19 Jun 2014 14:11:59 -0700 [thread overview]
Message-ID: <87d2e48uzk.fsf@tassilo.jf.intel.com> (raw)
In-Reply-To: <20140619125352.768e1ec9@redhat.com> (Jesper Dangaard Brouer's message of "Thu, 19 Jun 2014 12:53:52 +0200")
Jesper Dangaard Brouer <jbrouer@redhat.com> writes:
> I want to use/read the PMU counters for 'instructions' and 'cycles',
> from within the kernel, to measure the overhead of different in-kernel
> functions (and calc the pipeline efficiency ala perf-stat insns per cycle).
>
> What is the prefered way/API to read these counters, without
> conflicting with the perf tool?
>
perf_event_create_counter()
> I basically just need a in-kernel API to turn in these counters, and
> then I can just read them via the rdpcm instruction.
For RDPMC you would need extra support actually, as there is no
guarantee perf uses the fixed counter. In user space this
information is in the perf mmap page.
Also please be aware that RDPMC is not synchronizing.
-Andi
--
ak@linux.intel.com -- Speaking for myself only
next prev parent reply other threads:[~2014-06-19 21:12 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-19 10:53 Use of PMU counters inside kernel? Jesper Dangaard Brouer
2014-06-19 21:11 ` Andi Kleen [this message]
2014-06-20 11:04 ` Jesper Dangaard Brouer
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